摘要:
Methods and systems for stabilizing satellite spin about an intermediate inertia axis (Z) are disclosed. A set of gyros (22) sense the X component and the Y component of the angular velocity of the satellite body. A single degree of freedom momentum wheel (26) has a fixed transverse orientation with respect to the intermediate axis in order to store momentum. In one embodiment, the momentum wheel (26) is oriented to store momentum parallel to the Y axis. A tachometer (30) senses the rotation rate of the momentum wheel (26). A processor (24) forms a control signal representative of a control torque to be applied to the momentum wheel (26). The control torque is based upon the X component and the Y component of angular velocity of the satellite, and the angular velocity of the momentum wheel (26). These methods and systems may also be used to invert the spin direction of spinning satellites, ensure tumble recover to a preferred orientation, and stabilize the body spin axis against nutation, dynamic imbalance and external torques.
摘要:
A method, apparatus, article of manufacture, and a memory structure for controlling the eccentricity of an orbit. One embodiment of the present invention is described by a method comprising the step of performing a program of eccentricity control maneuvers wherein the control maneuvers are executed at times and in directions selected to apply substantially all eccentricity control along a line of antinodes. In one embodiment, the control maneuvers arc tangential maneuvers, and each control maneuver is applied near the line of antinodes. Provision is made for performing additional maneuvers, including node retargcting maneuvers during specified intervals. Another embodiment of the invention is described by a satellite in a substantially geosynchronous orbit having a satellite control system with a processor implementing instructions to perform control maneuvers as described above. Yet another embodiment of the present invention is described by a command facility comprising a processor for implementing instructions to perform the program control maneuvers described above, and a communicatively coupled transmitter for transmitting the commands to the satellite.
摘要:
Agile (electronically steerable) beam sensing with associated on-board processing, previously used exclusively for positioning of antennas for beam formation and tracking in communications systems, is now also used for satellite active attitude determination and control. A spinning satellite (100) is nadir oriented and precessed at orbit rate using magnetic torquing determined through use of an on-board stored magnetic field model (520) and attitude and orbit estimates (212). A Kalman filter (211) predicts parameters (202, 203) associated with a received signal (204) impinging on the satellite's wide angle beam antenna (201). The antenna system measures the error between the parameter predictions and observed values and sends appropriate error signals (207) to the Kalman filter for updating its estimation procedures. The Kalman filter additionally outputs the spacecraft attitude error signals (215) to an attitude control law (213), which determines commands to attitude-altering magnetic torque elements (220) to close the control loop via the spacecraft dynamics (230).
摘要:
In an exemplary embodiment, a pattern is recognized from digitized images. A first image metric is computed from a first digitized image and a second image metric is computed from a second digitized image. A composite image metric is computed as a function of the first image metric and the second image metric, and a pattern is identified by comparing the composite image metric against a reference image metric. The function may be a simple average or a weighted average. The image metric may include a separation distance between features, or a measured area of a feature, or a central angle between two arcs joining a feature to two other features, or an area of a polygon whose vertices are defined by features, or a second moment of a polygon whose vertices are defined by features. The images may include without limitation images of friction ridges, irises, or stars.
摘要:
A method and an apparatus for controlling the attitude and momentum of a spacecraft while deploying an appendage from the spacecraft. The method uses solar tacking and similar techniques to produce differential solar torques that are used to control the momentum and attitude of the spacecraft during the appendage deployment.
摘要:
A solar wing control system for avoiding thermal shock to a solar wing includes an eclipse exit slew profile generator having an eclipse exit slew rate output for rotating the solar wing from an eclipse exit angle to a solar power generation angle to control solar wing heating rate.
摘要:
A method for steering the payload beam of a satellite in a non-geostationary orbit toward an intended service area having known geographical dimensions in order to obtain improved pointing performance with a corresponding reduction in the demand on onboard hardware and software systems. The method comprises the steps of determining a subterranean target point and a direction fixed in the payload beam, calculating the orientation that points the payload beam direction through the subterranean target point, and maintaining this payload beam orientation using an on-board attitude control system.
摘要:
Structures and methods are provided to effect satellite maneuvers in the presence of disturbance torques with enhanced fuel efficiency. A thruster control loop is combined with a wheel control loop in which the wheels respond to an estimate of the disturbance torques (e.g., an angular acceleration estimate, a thruster torque command or a filtered thruster torque command) to create a counteracting gyroscopic torque. Simulations of the invention's methods have shown they have the authority of all-thruster control systems and fuel efficiency that rivals that that of all-wheel control systems.
摘要:
A method and system are disclosed for inverting a satellite spinning about a first desired spin axis to spin about a second desired spin axis substantially antiparallel to the first desired spin axis. A tumbling motion is induced in the satellite so that a spin axis of the satellite oscillates between the first desired spin axis and the second desired spin axis. The tumbling motion is induced by sensing at least one component of the angular rate vector and controlling a single degree of freedom momentum storage device based upon the at least one component of the angular rate vector. The single degree of freedom momentum storage device has an orientation of variation substantially perpendicular to the desired spin axis. The single degree of freedom momentum storage device is controlled so that the first desired spin axis is made an intermediate inertia axis of an effective inertia matrix. A capture point is detected at which the angular rate vector is sufficiently close to the second desired spin axis to be recaptured. After detecting the capture point, the single degree of freedom momentum storage device is controlled so that the angular rate vector substantially aligns with the second desired spin axis.
摘要:
Methods and systems for stabilizing satellite spin about an intermediate inertia axis (Z) are disclosed. A set of gyros (22) sense the X component and the Y component of the angular velocity of the satellite body. A single degree of freedom momentum wheel (26) has a fixed transverse orientation with respect to the intermediate axis in order to store momentum. In one embodiment, the momentum wheel (26) is oriented to store momentum parallel to the Y axis. A tachometer (30) senses the rotation rate of the momentum wheel (26). A processor (24) forms a control signal representative of a control torque to be applied to the momentum wheel (26). The control torque is based upon the X component and the Y component of angular velocity of the satellite, and the angular velocity of the momentum wheel (26). These methods and systems may also be used to invert the spin direction of spinning satellites, ensure tumble recover to a preferred orientation, and stabilize the body spin axis against nutation, dynamic imbalance and external torques.